Originally posted by tomUK
Is there anyway to tell if the unit I have is reporting the wrong figures?
I've not played with one of the bad hubs, but I believe that those who have run into this particular problem (after sending their hub in for repair) have found that the speed is grossly off as well. So, if you're confident that you've entered the correct wheel circumference yet the speed is reading way too high, then there's a good chance you've got a bad hub. If not, then I'd guess that it is probably okay.
If you really want to be certain, here's what to do:
1) put your bike in a trainer or some other stationary stand
2) shift your lowest gear
3) put the computer in torque mode (as if you were going to zero it)
4) with the cranks perfectly horizontal, apply a known force (e.g., your body weight - which requires excellent balance!) to the pedal
The torque that is reported by the computer should match the torque that is applied, once you correct/account for the crank length, the gear ratio, and get everything in the proper units. (See the FAQ of the wattage list on topica.com for more details of this "stomp test".) If it does, and the speed/distance reading is also correct, then the power data calculated from these two values (i.e., torque and rpm of the wheel) will also be correct.